The concept of non-impacting linear vibrators is known in the art, typically, a cylindrical mass oscillates back and forth in a cylindrical chamber as air flows into and out of the cylindrical chamber. Air or a fluid such as an air oil mist forms a fluid bearing that is used to support the cylindrical mass as it oscillates back and forth. While such systems provide vibration one of the difficulties with such systems is that the vibrators do not always start on-demand as the mass may stop on a dead center position where the fluid supplied to the cylindrical chamber might flow around the cylindrical mass without inducing the required oscillation of the mass. Another difficulty is that although the mass oscillates on a fluid bearing the fluid bearing the fluid bearing may not always prevent contact between the oscillating mass and the chamber walls thus causing damage to either the surface of the mass or the walls of the chamber or both which can render the vibrator inoperative.
In one embodiment of the known linear vibrators the vibrator includes a cylindrical shaped piston that is driven back and forth in a chamber by fluid that simultaneously pushes the piston back and forth as it forms an air bearing around the piston to provide essentially a frictionless surface between the piston and the housing. One of the drawbacks of such vibrators is that to ensure that the vibrator responds to the introduction of the fluid into the housing it is usually necessary to have some mechanical means such as a spring to bias the piston to facilitate initiation of the oscillating activity of the piston. That is, when fluid such as air is introduced into the chamber the piston, which is to be supported by an air bearing, might not immediately begin oscillating as air is introduced into the chamber. Consequently, if one wants to ensure vibrator start-up one needs to bias the piston to one end or the other end of the vibrator. The biasing is usually done through a mechanical device such as a spring or the like that is located at one end of the chamber in the vibrator. However, introducing mechanical start-up devices such as springs reduces the life of the vibrator since the springs eventuality break through metal fatigue.